我正在尝试使用标签进行全文搜索，但它对我来说不能正常工作，请查看附件图片
查询是：
SELECT *,
MATCH(tags) AGAINST ('tag3 tag6 tag4') AS score
FROM items
ORDER BY score DESC
为什么分数没有在正确的顺序字段中排序？如果您检查第二行有我搜索过的所有标签，而第一个字段没有 tag3 关键字。
我的意思是 id 字段顺序应该是：5,1,2 .. etc 而不是 1,5,2..etc
我的错误在哪里？
然后我想先在标签字段中搜索然后如果没有结果我想在描述字段中搜索与 FULLTEXT 相同的关键字，因此如果标签不匹配，用户将在标签和描述中搜索，是否可以在同一个查询中或者我需要两个单独的查询？
在这个文档http://dev.mysql.com/doc/refman/5.0/en/fulltext-natural-language.html中它说“对于非常小的表格，单词分布不能充分反映它们的语义价值，并且这个模型可能有时会产生奇怪的结果。”
如果你的 items 表很小——例如一个示例表——你可能会遇到这个问题并得到一个“奇怪”的结果。
您可能希望尝试此查询IN BOOLEAN MODE以查看您的结果是否与您的预测相符。尝试这个。
SELECT *,
MATCH(tags) AGAINST ('tag3 tag6 tag4' IN BOOLEAN MODE) AS score
FROM items
ORDER BY score DESC
布尔模式禁用词分布排名。请注意，您应该了解自然语言模式和布尔模式之间的区别，一旦您拥有一张合适大小的表格，就应该明智地选择使用哪一个。如果您正在搜索博客中包含的那种标签，布尔值可能是您的最佳选择。
首先，这是您在我的 Windows7 机器上加载到 MySQL 5.5.12 中的示例数据
mysql> DROP DATABASE IF EXISTS lspuk;
Query OK, 1 row affected (0.00 sec)
mysql> CREATE DATABASE lspuk;
Query OK, 1 row affected (0.00 sec)
mysql> USE lspuk
Database changed
mysql> CREATE TABLE items
-> (
-> id int not null auto_increment,
-> description VARCHAR(30),
-> tags VARCHAR(30),
-> primary key (id),
-> FULLTEXT tags_ftndx (tags)
-> ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.04 sec)
mysql> INSERT INTO items (description,tags) VALUES
-> ('the first' ,'tag1 tag3 tag4'),
-> ('the second','tag5 tag1 tag2'),
-> ('the third' ,'tag5 tag1 tag9'),
-> ('the fourth','tag5 tag6 tag2'),
-> ('the fifth' ,'tag4 tag3 tag6'),
-> ('the sixth' ,'tag2 tag3 tag6');
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql>
请查看标签填充在 MySQL 中发生的方式：
mysql> SELECT 'tag1',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag1%' UNION
-> SELECT 'tag2',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag2%' UNION
-> SELECT 'tag3',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag3%' UNION
-> SELECT 'tag4',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag4%' UNION
-> SELECT 'tag5',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag5%' UNION
-> SELECT 'tag6',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag6%' UNION
-> SELECT 'tag9',COUNT(1) tag_count FROM items WHERE tags LIKE '%tag9%';
+------+-----------+
| tag1 | tag_count |
+------+-----------+
| tag1 | 3 |
| tag2 | 3 |
| tag3 | 3 |
| tag4 | 2 |
| tag5 | 3 |
| tag6 | 3 |
| tag9 | 1 |
+------+-----------+
7 rows in set (0.00 sec)
mysql>
仔细看，请注意以下事实：
如果删除 tag4 并运行查询，则根本没有得分
mysql> SELECT *,MATCH(tags) AGAINST ('tag3 tag6') as score FROM items ORDER BY score DESC;
+----+-------------+----------------+-------+
| id | description | tags | score |
+----+-------------+----------------+-------+
| 1 | the first | tag1 tag3 tag4 | 0 |
| 2 | the second | tag5 tag1 tag2 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 |
| 4 | the fourth | tag5 tag6 tag2 | 0 |
| 5 | the fifth | tag4 tag3 tag6 | 0 |
| 6 | the sixth | tag2 tag3 tag6 | 0 |
+----+-------------+----------------+-------+
6 rows in set (0.00 sec)
评估方法似乎基于令牌字段的平均数量，并且特定顺序中特定值的存在和/或不存在会影响评分。如果您应用不同风格的评分和标签规范，请注意各种评分：
mysql> SELECT *,MATCH(tags) AGAINST ('tag3 tag6 tag4') as score FROM items ORDER BY score DESC;
+----+-------------+----------------+--------------------+
| id | description | tags | score |
+----+-------------+----------------+--------------------+
| 1 | the first | tag1 tag3 tag4 | 0.6700310707092285 |
| 5 | the fifth | tag4 tag3 tag6 | 0.6700310707092285 |
| 2 | the second | tag5 tag1 tag2 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 |
| 4 | the fourth | tag5 tag6 tag2 | 0 |
| 6 | the sixth | tag2 tag3 tag6 | 0 |
+----+-------------+----------------+--------------------+
6 rows in set (0.00 sec)
mysql> SELECT *,MATCH(tags) AGAINST ('tag3 tag6 tag4' IN BOOLEAN MODE) as score FROM items ORDER BY score DESC;
+----+-------------+----------------+-------+
| id | description | tags | score |
+----+-------------+----------------+-------+
| 5 | the fifth | tag4 tag3 tag6 | 3 |
| 1 | the first | tag1 tag3 tag4 | 2 |
| 6 | the sixth | tag2 tag3 tag6 | 2 |
| 4 | the fourth | tag5 tag6 tag2 | 1 |
| 2 | the second | tag5 tag1 tag2 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 |
+----+-------------+----------------+-------+
6 rows in set (0.00 sec)
mysql> SELECT *,MATCH(tags) AGAINST ('+tag3 +tag6 +tag4' IN BOOLEAN MODE) as score FROM items ORDER BY score DESC;
+----+-------------+----------------+-------+
| id | description | tags | score |
+----+-------------+----------------+-------+
| 5 | the fifth | tag4 tag3 tag6 | 1 |
| 1 | the first | tag1 tag3 tag4 | 0 |
| 2 | the second | tag5 tag1 tag2 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 |
| 4 | the fourth | tag5 tag6 tag2 | 0 |
| 6 | the sixth | tag2 tag3 tag6 | 0 |
+----+-------------+----------------+-------+
6 rows in set (0.00 sec)
mysql>
解决方案似乎是评估 BOOLEAN MODE 分数，然后评估非 BOOLEAN MODE 分数，如下所示：
SELECT *,
MATCH(tags) AGAINST ('tag3 tag6 tag4') as score1,
MATCH(tags) AGAINST ('+tag3 +tag6 +tag4' IN BOOLEAN MODE) as score2
FROM items ORDER BY score2 DESC, score1 DESC;
这是针对您的示例数据的结果：
mysql> SELECT *,
-> MATCH(tags) AGAINST ('tag3 tag6 tag4') as score1,
-> MATCH(tags) AGAINST ('+tag3 +tag6 +tag4' IN BOOLEAN MODE) as score2
-> FROM items ORDER BY score2 DESC, score1 DESC;
+----+-------------+----------------+--------------------+--------+
| id | description | tags | score1 | score2 |
+----+-------------+----------------+--------------------+--------+
| 5 | the fifth | tag4 tag3 tag6 | 0.6700310707092285 | 1 |
| 1 | the first | tag1 tag3 tag4 | 0.6700310707092285 | 0 |
| 2 | the second | tag5 tag1 tag2 | 0 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 | 0 |
| 4 | the fourth | tag5 tag6 tag2 | 0 | 0 |
| 6 | the sixth | tag2 tag3 tag6 | 0 | 0 |
+----+-------------+----------------+--------------------+--------+
6 rows in set (0.00 sec)
mysql>
或者您可以尝试不使用加号
mysql> SELECT *,
-> MATCH(tags) AGAINST ('tag3 tag6 tag4') as score1,
-> MATCH(tags) AGAINST ('tag3 tag6 tag4' IN BOOLEAN MODE) as score2
-> FROM items ORDER BY score2 DESC, score1 DESC;
+----+-------------+----------------+--------------------+--------+
| id | description | tags | score1 | score2 |
+----+-------------+----------------+--------------------+--------+
| 5 | the fifth | tag4 tag3 tag6 | 0.6700310707092285 | 3 |
| 1 | the first | tag1 tag3 tag4 | 0.6700310707092285 | 2 |
| 6 | the sixth | tag2 tag3 tag6 | 0 | 2 |
| 4 | the fourth | tag5 tag6 tag2 | 0 | 1 |
| 2 | the second | tag5 tag1 tag2 | 0 | 0 |
| 3 | the third | tag5 tag1 tag9 | 0 | 0 |
+----+-------------+----------------+--------------------+--------+
6 rows in set (0.00 sec)
mysql>
无论哪种方式，您都必须同时合并 BOOLEAN MODE 和 non-BOOLEAN 模式。
将order修改为按score DESC, id DESC 排序。
假设分数值相同，则首先显示5的行。